Coating compositions that exhibit hydrophilic properties are often desirable for certain coating applications, such as where coated surfaces exhibiting anti-fouling, easy-to-clean, self-cleaning, and/or anti-fogging properties are desired. Such coatings can be particularly useful, by way of example, for application to surfaces exposed to the outdoor environment. Building structures, automobiles, and other articles that are exposed to the outdoors are likely to come in contact with various contaminants, such as dirt, oil, dust, and clay, among others. A surface with a hydrophilic coating deposited thereon may be self-cleaning because the coating has the ability to wash those contaminants away when the surface comes in contact with water, such as during a rainfall.
In view of these and other advantages, various hydrophilic coating compositions have been proposed. Many of these coatings achieve their hydrophilicity through the action of a photocatalytic material, such as titanium dioxide. The use of such materials can, however, in at least certain applications, be problematic. For example, when applying such a material over an organic film, such as a typical coating composition used in automotive applications, the photocatalytic material may contact the organic film. Because an —OH free radical is generated by the photocatalytic action of a photocatalytic material, the underlying organic film is susceptible to degradation.
As a result, it would be advantageous to provide a coating composition that can produce thin coating films that exhibit hydrophilic properties and, therefore, self-cleaning properties. Furthermore, it would be desirable to provide such compositions that do not necessarily rely on the use of a photocatalytic material to produce such properties.